snow line

WordReference Random House Unabridged Dictionary of American English © 2025

snow′ line′, 

1. Meteorology the line, as on mountains, above which there is perpetual snow.
2. Meteorology the latitudinal line marking the limit of the fall of snow at sea level.
• 1825–35

Collins Concise English Dictionary © HarperCollins Publishers::

snow line, snowline / ˈsnəʊˌlaɪn/ noun

1. the altitudinal or latitudinal limit of permanent snow